The present invention relates generally to power amplifiers and, more particularly, to electronically tuned power amplifiers.
Power amplifiers boost a low-power signal to a higher power level, to be delivered to a load. The load determines the gain, linearity, and efficiency of the amplifier. Having the ability to dynamically vary this load impedance allows the properties of the amplifier to be dynamically varied.
Current techniques for tuning power amplifiers include mechanical tuning, tuning using electrically variable capacitors or inductors, and injecting a carrier signal using a circulator. Mechanical tuning is employed in “cavity” amplifiers, which include mechanical cavity tuning controls. Here tuning is carried out by mechanically adjusting a cavity dimension. Mechanical tuning is usually slow and cumbersome.
The above-noted electrical tuning techniques (variable capacitors or inductors and injecting a carrier signal using a circulator), in general, allow for more rapid amplifier tuning than the mechanical adjustment method. However, these methods are typically suitable only for narrow band applications. Circulators, for example, have relatively narrow bandwidths and are therefore unsuitable for tuning in broad band applications.
Thus, there is a need for a power amplifier that includes a tuning system that is suitable for broadband applications.